1. Field of the Invention
The present invention relates to a slide guide unit used for a semi-conductor inspection apparatus, etc. which linearly guides a movable body such as a table mounted on a slider along a track rail and, more specifically, the invention relates to a slide guide unit a screw shaft for linearly driving the slider is screwed in the slider so as to pass therethrough.
2. Description of a Related Art
As a slide guide unit of this type, the unit disclosed in Japanese Patent Laid-Open No. 273550/1997 is known. The slide guide unit includes a track rail formed in the shape of a channel with a concave groove and having a slide guide surface formed along the length thereof, a screw shaft disposed in the concave groove along the length of the track rail, and a slider including a sliding contact member to be in contact with the slide guide surface of the track rail and a nut member to be screwed onto the screw shaft, wherein in case where the screw shaft is rotated for example by a motor, the slider moves within the concave groove of the track rail according to the amount of revolution so that the turns of the screw for the movable body, such as a table, mounted on the slider to be guided in any given motion in either direction are precisely determined.
The slider is movably supported by sliding contact between its sliding contact member and the sliding guide surface of the track rail. The sliding contact member is made of an abrasion resistant material such as a resin containing carbon fiber, ceramic, or sintered alloy. The Japanese Patent Laid-Open No. 273550/1997 suggests that the sliding contact member be bonded to the slider at a position facing the slide guide surface on the track rail, and in case where a resin material such as a carbon fiber dispersed in resin or a metallic powder dispersed in resin is used to form the sliding contact member, it may be modeled on the slider by injection molding.
On the other hand, the nut portion for converting the rotational movement of the screw shaft into the linear movement of the slider is provided with an internal thread to be in sliding contact with the external thread formed on the screw shaft, and is made of an abrasion and load resistant material. The nut member is bonded to the through hole provided on the slider.
In the slide guide unit having such a structure, since a driving force along the track rail is applied from the nut portion screwed onto the screw shaft to the slider, and the slide is supported in free reciprocating motion by sliding contact with the sliding contact pad of the track rail, the nut member and the sliding contact member have to be firmly fixed to the slider so as not to become detached from the slider.
However, in the slide guide unit described in Japanese Patent Laid-Open No. 273550/1997, since the nut member and the sliding contact member are fixed to the slider only by an adhesive, there is apprehension that the nut member or the sliding contact member may become detached from the slider accidentally due to a large force applied in the direction of travel of the slide to the nut member or the sliding contact member in the event that the direction of travel of the slider is suddenly reversed.
In order to fix the nut member and the sliding contact member to the slider so that they resist such a force, a pair of lid bodies can be fixed for example by bolts to the front and rear end surfaces of the slider so that the lid bodies hold the nut member and the sliding contact member on the slider. However, providing such lid bodies on the slider results in the expenditure of time and effort to assemble the slider, increase in the number of components, and thus increase in cost. In addition, when the lid bodies are fixed on the front and rear end surfaces of the slide as described above, the length of the slider increases by the length corresponding to that of the lid bodies, thereby the size of the unit itself increases with respect to the amount of stroke of the slider in its reciprocating motion.